1. Field of the Invention
The present invention relates to an image capture apparatus and a control method therefor.
2. Description of the Related Art
Conventionally, electronic still cameras and video cameras use an automatic focus adjustment (autofocus or AF) method in which the position of a focus lens that maximizes high-frequency components of luminance signals acquired from an image sensor provided with a CCD (charge-coupled device) and the like is the in-focus position. This method is also referred to as a contrast detection method.
In order to search for the in-focus position (scanning), image capture is performed while driving the focus lens in a focus detection range (for example, from the near end to the far end). Then, evaluation values based on high-frequency components of luminance signals acquired from the image sensor (also referred to as focus evaluation values) are obtained and stored in correspondence with positions of the focus lens.
The focus evaluation values are not obtained for the entirety of an image, but for focus detection areas (hereinafter referred to as AF frames) that are set in the vicinity of the center of a screen or in the vicinity of detected subject areas. The position of the focus lens corresponding to the maximum focus evaluation value of the AF frames (hereinafter also referred to as a peak position) is determined as the in-focus position.
The resultant focus thus achieved at the time of AF is used to determine the in-focus position during image capture, and may further be used in determination associated with image capture processing and with image processing in the case where the distribution of distances in the screen is acquired by setting a plurality of AF frames.
According to the disclosure of Japanese Patent Laid-Open No. 2012-4716, distance information of each subject is acquired, an image is divided into areas of subjects located in the foreground and areas of subjects located in the background, and scene determination and image processing based on the result of scene determination are executed for each divided area. This document also discloses generation of distance information (range images) of subjects included in a captured screen based on the high-frequency components of an image acquired while moving the focus lens.
On the other hand, according to the disclosure of Japanese Patent Laid-Open No. 2006-162724, distances to subjects are measured in a plurality of AF frames, and if the subject distances satisfy predetermined conditions for starting focus bracketing, image capture operations corresponding to the satisfied conditions are executed.
However, if a scene with a large depth of field is divided into areas based on subject distances, the accuracy of area division is lowered due to a small difference among the subject distances acquired in the plurality of AF frames. Meanwhile, in the case of a planar subject with no practical difference in distance, even though the distance-based area division cannot be performed in reality, there is a possibility that erroneous area division is performed due to variation in the acquired subject distances.
The method described in Japanese Patent Laid-Open No. 2012-4716 does not evaluate the accuracy of area division based on information of subject distances, and therefore gives rise to the possibility that erroneous area division is performed in a scene with a small difference among subject distances.
On the other hand, while the method described in Japanese Patent Laid-Open No. 2006-162724 determines the in-focus distance for bracketing upon identification of a scene for which focus bracketing is effective, it does not perform area division based on subject distances, and therefore does not execute image processing and image capture processing for each area.
In the case where a scene has changed, distance information of subjects prior to the change of the scene should not be used as-is; however, Japanese Patent Laid-Open No. 2012-4716 and No. 2006-162724 do not take into consideration a change in the reliability of subject information caused by a change in a scene.